Set RenderAutoHideSurfaceAreaLimit to a lower value, and base it on GPU capabilities.

[Dan-Linden]

I recently became aware of the RenderAutoHideSurfaceAreaLimit debug setting and see it could be quite useful for blocking objects that have excessive surface area from bogging down the renderer.
In my brief testing I found the setting's default value of 10 million is of little use. 1000 seems the right order of magnitude to block the griefer objects that abuse overdraw while allowing everything else to render as normal. My testing was done with some griefer objects on private region http://maps.secondlife.com/secondlife/Danger!%20Danger!/216/32/39

This debug setting could be a really useful parameter to use in the Improve Graphics Speed floater. It does need to be based on GPU capability as graphics cards may someday be able to render the 10 million (of whatever units) this setting uses.

Test Plan

• Verify "sim-surrounds" and other large objects render correctly when this value is set to Default.
• Toggle this feature between off (value = 0) and Default and verify there is no visual different.
• Verify objects that have excessive surface area do not bog down the renderer to single digit FPS. (eg. http://maps.secondlife.com/secondlife/Danger!%20Danger!/216/32/39)